1. Field of the Invention
Embodiments of the present invention relate to a semiconductor device and a method for fabricating a semiconductor device. More particularly, embodiments of the present invention relate to a semiconductor device capable of maintaining constant insulation breakdown voltage and a method of fabricating the same.
2. Description of the Related Art
In general, program and erase functions in a conventional memory device, e.g., an electrically erasable programmable read-only memory (EEPROM), may require a high voltage to be boosted to a predetermined level, e.g., 10V or a higher voltage. Such voltage control may be achieved by using a word line voltage generating circuit having a pumping circuit and a clamping circuit. The clamping circuit may include a semiconductor device, e.g., a clamp diode, employing an insulation breakdown voltage (BV) to perform clamping. However, the conventional clamp diode may exhibit a walkout occurrence.
More specifically, the walkout occurrence refers to a phenomenon, where a reverse bias in the conventional clamp diode may cause a junction avalanche breakdown, so that hot carriers generated in a depletion region of the clamp diode may be trapped in a silicon oxide layer thereof. Such an occurrence may weaken the electric field at the junction of the clamp diode, thereby increasing the insulation BV. However, an increased insulation BV may induce an increase in an output voltage in a gate electrode of a high voltage transistor, i.e., a select transistor of the memory device, e.g., above about 1V. Further, an increased insulation BV may increase an electric field of the gate electrode, which in turn, may trigger punch-through occurrences and increased leakage current in the clamp diode. As such, a memory device controlled by the conventional clamp diode may have reduced reliability, e.g., increased limitations in EEPROM devices that program in page mode.